Tub mixer



FIG. 1 is a front perspective view of a tub mixer showing our new design;

FIG. 2 is a right side elevational view thereof, the left side elevational view being a mirror image thereof;

FIG. 3 is front elevational view thereof;

FIG. 4 is a rear elevational view thereof; and,

FIG. 5 is a top plan view thereof.

The broken lines in the Figures are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a tub mixer, as shown and described. 